An AutoStar Suite Software CD-ROM is included as standard equipment with each LXD-75, LX90, and LX200 telescope. This software package integrates the telescope with a Windows-based PC or laptop computer for an enhanced range of performance features. It includes a planetarium program with a database of 19,000,000 stars and deep space objects for display on your computer screen. All of the best on-screen display and star chart-printing features of a standard planetarium program are included for stand-alone use when nights are cloudy, or for planning observing sessions.

The software lets you enable or disable the Hubble Guide Star Catalog; set the on-screen Viewpoint to go to the current zenith or any R.A. and Dec. coordinate; choose any object by catalog name or number; enable or disable custom catalogs; add new catalogs; set magnitude limits; flip the star map for correct orientation as you observe through the telescope; zoom the star map display from 180° down to tiny fractions of an arc second; adjust label fonts and colors, coordinate grid colors, and brightness and contrast; enable or disable the night vision mode; and more.

In addition, if you connect the scope to your computer, the program lets you click on objects in the sky map that is displayed on the computer screen and have your telescope automatically slew to those objects. You can automatically generate AutoStar Tours of favorite objects with a simple point and click, as well as using the program to keep observing logs.

The software lets you control all AutoStar functions from your computer or laptop. You can use it to create observing lists and download them to the AutoStar for use in the field when you don’t have your computer or laptop with you. “Talking Telescope” software (included) converts AutoStar text displays to synthesized speech through your computer’s speaker. An AutoStar Update Tool in the software keeps your AutoStar II computer hand control current by downloading the latest system firmware updates and comet, asteroid, and satellite data from the internet.

You can also use the software to control your telescope remotely via the internet. Designed to be the ultimate platform for remote digital astronomy with your Meade telescope, the AutoStar Suite Astronomer’s Edition contains tools for dome controls, weather sensors, and other functions required for this purpose. You can reach your telescope and dome through a single network connection. You can then communicate via an IP address, using the AutoStar Net Scope program to control the entire observatory over the Internet. This solves the biggest problem in setting up for remote access to your telescope – the problem of your distance from the scope itself. You can be in your living room to control the scope in your backyard, or just as easily, control a friend’s system in another country!

The minimum computer requirements for installing the AutoStar Suite Software are a PC running Windows 98SE or later, with a minimum of 64 MB of RAM, and 200 MB of free hard disk space.

GPS/AutoStar computer operation: The operation of an LX200 is simplicity itself. Once you mount the scope on its tripod, you simply turn it on. An integrated true-level electronic sensor levels the optical tube parallel to the ground. A 16-channel GPS (global positioning satellite) receiver in the left fork arm uses a network of earth-orbiting government satellites to first quickly triangulate the scope’s position on the earth with an accuracy measured in meters, then determine the time to fraction of a second accuracy. A built-in electronic compass automatically rotates the scope optical tube to aim it due north (the home position). This is a tremendous help if trees or buildings block your view of the north. Built-in software compensates for magnetic declination errors (the difference between true north and magnetic north at your observing location). Once the scope reaches the home position (it only takes a minute or two), press the “enter” button on the AutoStar II hand controller to start the astronomical alignment. The LX200 slews at 8° per second to the first of two alignment stars (6° per second in the case of a 16” scope). If that star is not precisely centered, a touch or two on the AutoStar II hand control directional push buttons quickly centers it. Do the same with the second alignment star the scope moves to and you’re ready to observe. That’s it! For the rest of the evening, a computer in the AutoStar II controls the scope’s altitude and azimuth motors to keep you precisely centered on whatever you aim at, for as long as you want to observe. It takes only a few moments to begin observing, since you never have to line up on the celestial pole, take the time to precisely level the tripod, input observing latitude and longitude and accurate local time, or adjust imprecise manual setting circles to match the sky.

AutoStar II computer: This scope’s AutoStar II computer can show you the planets and thousands of deep space objects the very first night you use your scope – even if you’ve never used a telescope before! The computer’s 3.5 megabyte flash memory (which you can upgrade at any time for free via the internet) contains the following objects:

the entire NGC (New General Catalog) of 7840 nebulas, galaxies, and star clusters

the IC (Index Catalog) of 5386 nebulas, galaxies, and star clusters

the Messier Catalog of the 110 best known deep sky objects

the Caldwell Catalog of 109 fascinating objects that Messier missed

227 named objects

the Herschel Catalog of 400 faint and difficult deep sky objects

the Abell Catalog of 2712 galaxy clusters

the Arp Catalog of 645 irregular galaxies

the Uppsala Galaxy Catalog of 12,940 galaxies

a portion of the Russian Morphological Catalog listing 12,939 of its 30,642 galaxies down to magnitude 15

the General Catalog of 28,484 variable stars

the SAO and Hipparcos Star Catalogs of 31,090 stars

Also included are the eight major planets out to Pluto, the Moon, asteroids, comets, Earth satellites, and more. You can also add your own selected favorite deep sky objects in a separate catalog. The AutoStar II computer keeps a total database of 147,541 stars and objects in its memory for you to observe. Granted, a good number of the faintest objects will not be visible in the smaller aperture telescopes (for example, the 14th through 15th magnitude galaxies of the Russian Morphological Catalog are not eyepiece objects in an 8” scope that has a visual limiting magnitude of 14 under perfect dark sky seeing conditions), but they are all photographable with any of the telescopes given the right equipment and a modicum of persistence. Simply call up any of these 147,541 discrete objects on the AutoStar II hand control’s two line/sixteen character night-vision red screen by using the 20-button numeric keypad. Then press the “go-to” key. The LX200 slews to that object at a fast 6° to 8° per second (barely 11 seconds to go from horizon to zenith). The telescope quickly centers your chosen object in the field of view for you to enjoy. It routinely centers objects with an accuracy that puts them well within the field of the standard equipment eyepiece (usually within two arc minutes of dead center). The supplied Smart Mount Technology system (see below) can improve that accuracy still further. Once the object is located, the hand control screen tells you its catalog number, type, magnitude, size, right ascension, and declination. If you have the coordinates of an object not in the computer’s memory (a comet or asteroid, for example), enter those coordinates, press “go-to,” and your LX200 takes you there at speeds of up to 8° per second, as well. You can find faint deep space objects almost faster than you can read about it. If you want to scan the skies on your own, the AutoStar II keypad lets you move the scope in any direction at any of nine scanning and centering speeds up to 8 degrees per second. The AutoStar II computer includes an RS232 serial port for interfacing with a Windows-equipped computer. This allows remote control of the scope, as well as the ability to upgrade the operating system and database at any time at no cost through Meade’s website. The scope hand control provides brightness control of the computer keypad, a real-time digital readout of the telescope position in right ascension and declination, and a variety of other unique keypad/display panel functions.

Smart Drive: The LX200 has built-in dual-axis Smart Drive permanent periodic error correction (PPEC) to make deep space photography easier. This computer circuit automatically corrects for the minor drive errors present in every telescope – regardless of size, brand, or cost. It reduces by up to 90% the number of guiding corrections needed to compensate for those errors during long exposure photos. Simply use an optional illuminated reticle eyepiece to guide once on a star for a short time. Use the AutoStar hand control to make the corrections needed to keep the star centered on the eyepiece crosshairs. The Smart Drive remembers those corrections and automatically plays them back whenever the telescope is operating – virtually eliminating repetitive corrections during astrophotography. The dual-axis Smart Drive even corrects for declination errors, not just right ascension errors as with competitive scopes.

SMT (Smart Mount Technology): This standard equipment software program provides improved (and constantly improvable) pointing accuracy with the LX200. The already high pointing accuracy of the telescope is further refined with every object that you center precisely and synchronize on during a night’s observing. The program works in both altazimuth and equatorial modes. It includes a simple routine to refine the pointing accuracy for the entire sky with your particular equipment configuration and alignment. The refined pointing data can be saved and reused for permanent and portable setups.

Home Pulse Acquisition on 16” Models: Included as standard equipment with all 16” LX200 models, and unique among commercial telescopes, is a special “home pulse” feature that allows the telescope’s operating system to maintain the telescope’s pointing position in non-volatile memory, even when the telescope is turned off. This allows the telescope to be remotely aligned and operated over a long distance (even thousands of miles), by using a modem link to the telescope’s RS-232 serial interface. In this way Meade 16” LX200 telescopes may be operated through a pre-programmed sequence of, for example, CCD imaging, without a human operator being present in the observatory.

The mount’s drive base is made of heavy-duty die-cast aluminum, as are the dual fork arms that support the optical tube. The fork arms are shaped to damp vibrations quickly. There is a carrying handle on each fork arm. An adjustable bracket to hold the Autostar computer hand control can be attached to either carry handle, for convenient hands-free viewing of the computer display and operation by either a right-handed or left-handed observer. Both manual and electric slow motion controls are provided in both right ascension and declination. Analog setting circles are provided on the mount (5” in declination and 8.75” in right ascension), in addition to the digital r.a. and dec readouts on the Autostar computer hand control. The drive base has a 7-port multi-function control panel, including two RS-232 serial interface ports for communication with an external computer and other ancillary equipment.

The mount includes servo-controlled 12VDC slewing and tracking motors with 5.75” worm gear drives in both altitude and azimuth. The declination axis is supported by three 1.83” diameter ball bearings. Two ball bearings (one 4” and one 2.25”) provide smooth motion in right ascension. The drive system has 185 individually selectable drive speeds in both right ascension and declination to permit observatory-level precision in tracking, guiding, and slewing. You can choose from 0.01x to 1.0x sidereal, variable in 0.01x increments; 2x, 8x, 16x, 64x, or 128x the sidereal rate; as well as 1°/sec. to 8°/sec., variable in 0.1° increments. You can select either a sidereal or lunar tracking rate, or you can custom-select a drive speed from 2000 incremental rates to match solar or planetary motions.

The scope is powered by eight user-supplied C-cell batteries that fit into the fork arms. You don’t need an external battery pack or AC power supply as you do with competitive GPS scopes. Battery life is typically about 20 hours in warm weather, decreasing as the amount of slewing increases or as the temperature drops. Optional adapters (with 25' cords) are available to allow you to power the scope from 110-120 volt 60 Hz AC household current in your back yard to conserve battery life, or to power the scope from your car's cigarette lighter plug or a rechargeable battery for extended use in the field.

Advanced Coma-Free catadioptric designed to emulate the optical performance of a Ritchey-Chrétien telescope: The traditional two-mirror Ritchey-Chrétien (RC) design uses approximately hyperbolic primary and secondary mirrors to produce images that are free from coma over a wide field. Because of this wide coma-free field and a relatively fast focal ratio, the Ritchey-Chrétien design is particularly well suited to astrophotography. The RC is the design of choice for most of the major professional observatory telescopes built in the last half-century. For example, the Hubble Space Telescope and the twin 10-meter Keck telescopes in Hawaii are Ritchey-Chrétiens. However, because of the complexity of fabricating and testing a large aperture hyperbolic mirror (just ask the people who built the initially-flawed, but not discovered until it was in space, Hubble Space Telescope), traditional two-mirror Ritchey-Chrétiens are very expensive to manufacture and purchase, too expensive for many amateur astronomers. To emulate the coma-free performance of a true RC telescope, while keeping the cost within reason, the LX200-ACF Advanced Coma-Free (ACF) catadioptric optical system uses a full aperture aspheric corrector lens in conjunction with a simple spherical primary mirror. This creates a two-element primary mirror system that performs like an RC’s single hyperbolic primary mirror from the optical point of view of the LX200-ACF secondary mirror. The hyperbolic secondary mirror itself is mounted directly on the rear of the corrector lens, rather than in the traditional RC’s conventional spider vane assembly. This eliminates the image-degrading diffraction spikes of the secondary mirror support structure visible in commercial RC scope images. The result is RC-class coma-free wide-field performance in the LX200-ACF, at about a fourth the cost of most true RC systems. The corrector-modified design would itself be expensive to fabricate were it not for Meade’s more than a quarter-century of experience making Schmidt-Cassegrain correctors, which are in the same optical family as the corrector needed for the coma-free design of the LX200-ACF. An additional benefit of the full aperture corrector in the ACF design is slightly better correction for astigmatism than the traditional RC design. In addition, the LX200-ACF, due to its front corrector plate, is a closed tube design. This keeps the primary optical components protected from dust, moisture and other contaminants that might fall on the optical surfaces of the primary and secondary mirrors as can happen with the traditional open-tube RC design. While the LX200-ACF may not be a traditional RC design, its performance is RC-like in all important characteristics. A review in Sky & Telescope magazine of the predecessor of the Meade ACF optics said the bottom line is that the optics do “indeed perform like a Ritchey-Chrétien.” Another such review, in Astronomy magazine said, “This scope delivers Ritchey-Chrétien-like performance at a fraction of the cost.”

Oversized primary mirror: The diameter of the primary mirror of each LX200-ACF is larger than the diameter of the corrector lens at the front of its optical tube that admits the light. The primary mirror of the 8” scope is actually 8.25” in diameter, compared to the 8” diameter of the corrector lens. The 10” primary is 10.375” in diameter; the 12” is 12.375”; the 14” is 14.57”; and the 16” primary is 16.375” in diameter. Oversizing the primary mirror in this way gives you a wider fully-illuminated field than a conventional catadioptric scope whose corrector and primary mirror are the same size. The result is a gain of 5% to 8% more off-axis light available to your eye or camera, depending on the telescope model.

Fully multicoated UHTC (Ultra High Transmission Coatings) optics: The primary and secondary mirrors are vacuum-coated with aluminum, enhanced with multiple layers of titanium dioxide and silicon dioxide for increased reflectivity. A overcoating layer of durable silicon monoxide (quartz) assures long life. A series of anti-reflective coatings of aluminum oxide, titanium dioxide, and magnesium fluoride are vacuum-deposited on both sides of the full aperture corrector plate. These antireflection multicoatings provide a high 99.8% light transmission per surface, versus a per-surface transmission of 98.7% for standard single-layer coatings. Overall light throughput (the amount of light collected by the objective lens that actually reaches your eye or camera) is approximately 89% at the focal plane. UHTC multicoatings provide a 15% increase in light throughput compared with standard single-layer coatings. They effectively add the equivalent of 15% extra light-gathering area to the performance of a scope with standard coatings. It’s the equivalent of three-quarters of an inch of extra aperture in the case of a 10” scope, for example, but with no increase in actual size or weight. UHTC coatings also improve contrast, for lunar and planetary images that appear sharper and more crisply defined.

Fully baffled optics: A cylindrical baffle around the secondary mirror, in combination with the cylindrical baffle tube projecting from the center of the primary mirror, prevents stray off-axis light from reaching the image plane. In addition, a series of field stops machined into the inner surface of the central baffle tube effectively eliminates undesirable light which might reflect from the inside surface of the tube. The result of these baffle systems is improved contrast in lunar, planetary, and deep space observing alike.

Mirror lock: A progressive tension lock knob on the rear cell locks the telescope’s primary mirror rigidly in place once an approximate manual focus has been achieved. The standard equipment electric focuser, described below, is then used for fine focusing. Locking the mirror eliminates the possibility of mirror shift (the image moving from side to side while focusing, caused by the primary mirror tilting on the central baffle tube as the mirror moves fore and aft along the tube). Mirror shift, once the bane of CCD astrophotographers because it could easily move the image off a small CCD chip, is non-existent with the Meade system.

Electric focuser: The supplied zero image-shift electric microfocuser is controlled by the Autostar II computer hand control. It moves an externally-mounted eyepiece or camera to focus, rather than moving the primary mirror. This eliminates mirror shift during precise image centering and focusing for CCD applications. The microfocuser has four different operating speeds, from very fast down to an extremely slow creep, giving you focusing accuracy to a truly microscopic level during critical visual and astrophotographic applications. The focuser is designed to hold 2” star diagonals and eyepieces. A supplied 1.25” adapter allows the use of 1.25” diagonals and eyepieces in the 2” focuser. Another supplied adapter duplicates the 2” rear cell thread used on Schmidt-Cassegrain telescopes to allow the use of off-axis guiders, T-adapters, etc. A 1.25” visual back is not supplied with the scope. If you want to do high magnification eyepiece projection photography of the Moon and planets, you will have to add an optional 1.25” visual back #9135 and a tele-extender to the focuser’s supplied 2” rear cell thread adapter.

The Meade 12” LX200-ACF catadioptric telescope has Advanced Coma-Free optics to bring the astronomical image quality of a professional observatory to your back yard, at a down-to-earth price. It has a coma-free field similar to that of the Ritchey-Chrétien design optics used in most professional observatory telescopes and the Hubble Space Telescope, but at a fraction the cost of a true Ritchey-Chrétien of similar aperture.

If you have the dark skies to take full advantage of its immense light gathering capacity (two and a quarter times that of an 8” scope), or are willing to make the effort to transport this rather heavy scope to the dark sky site it needs for best performance, it’s a scope that can keep you happily observing and photographing the wonders of the heavens for the rest of your life. The 12” LX200-ACF has all the useful features you need to cater to virtually every observing need you might have.

Eyepiece: 1.25” 26mm Series 4000 Super Plössl (117x). The eyepiece field of view is 0.43° (over 85% the width of the full Moon), for expansive lunar and deep space views.

This Telescope’s Mount . . .

Fork mount/drive system: Drive base and dual fork arms of die-cast aluminum. The mount includes servo-controlled 12VDC slewing and tracking motors in both altitude and azimuth. The motors are powered by eight user-supplied C-cell batteries that fit into the fork arms. Optional adapters (with 25’ cords) are available to power the scope from 110-120 volt 60 Hz AC household current in your back yard to conserve battery life, or to power the telescope from your car’s cigarette lighter plug or a rechargeable battery for extended use in the field. For more details, click on the “mount” icon above.

GPS/Autostar computer: A 16-channel GPS (global positioning satellite) receiver is built into the top of the telescope’s left fork arm. The GPS receiver, in conjunction with a built-in electronic compass and Autostar computer control, automatically aligns the scope on the sky so that the Autostar computer can locate for you the more than 145,000 stars and objects in its memory. In addition to quickly and automatically moving the scope to any desired object (with an accuracy typically in the two arc minute range) and flawlessly tracking the object while you observe at your leisure, the Autostar computer provides numerous visual, tracking, and photographic tools and functions to make your observing easier and more enjoyable.

Unique “Smart Mount” technology can constantly improve the already high pointing accuracy of the telescope with every object that you center precisely and synchronize on during a night’s observing. For more details on these features, click on the “computer” icon above.

Adjustable height tripod: The 50 lb. giant field tripod adjusts from a height of 40” to 50” and damps vibrations quickly. It has 3” diameter steel legs, with a center leg brace for rigidity. Six 1.25” diameter holes in the leg brace can hold eyepieces while observing. A single threaded rod with a large hand-tighten knob simultaneously holds the scope firmly on the tripod and locks the legs rigidly in the most stable position.

AutoStar Software Suite: This standard equipment software package is designed to integrate the telescope with your Windows-based PC or laptop computer for an enhanced range of performance features. The AutoStar Software Suite includes a planetarium program with a database of 19,000,000 stars and deep space objects for display on your computer screen. It includes all the standard planetarium program features for stand-alone use when nights are cloudy. In addition, it contains programs for controlling the telescope from your laptop or PC. For more details on the many capabilities and features of the AutoStar Software Suite, click on the “software” icon above.

What can you see through an 12” LX200-ACF with Advanced Coma-Free UHTC optics?

With the 15% higher light transmission of UHTC optics and two and a quarter times the light gathering capacity of an 8” scope (45% more than a 10”) for a visual limiting magnitude of approximately 15, this scope’s 12” coma-free flat-field optics give the Universe an astonishing depth, dimension, and grandeur at dark sky sites. The Orion Nebula grows to twice the area you see through an 8” scope, with subtle color variations becoming visible. Jupiter becomes an interlocking web of fine structural detail, with shadowy detail often visible on the surface of its largest moon, Ganymede. Faint galaxies and planetary nebulas, barely visible blurs in smaller scopes, often reveal structure during visual observing that rivals that in long exposure observatory photos. Densely packed globular clusters are usually resolved to their core. Open clusters show stars that are sharp and point-like all the way across the field thanks to the flat field of its unique Advanced Coma-Free optics. With a photographic limiting magnitude of 17.5, all of it can be photographed in superlative detail (and with surprisingly short exposure times) by adding a few inexpensive accessories.

The altazimuth drive of the LX200-ACF is more than accurate enough for piggyback, lunar, and planetary 35mm photos and much CCD imaging. However, field rotation causes stars at the corners of an image to streak during exposures longer than five minutes if a field derotator or an equatorial wedge isn’t used to align the scope on the celestial pole. So, if you plan on doing deep space photography, you’ll need to add either an optional #1220 field derotator or an optional #2575 X-wedge to the 12” LX200-ACF.

This 12” scope will perform quite nicely on faint deep space objects such as galaxies and nebulas under mildly light-polluted suburban skies, if it is provided with the proper light pollution filter. However, truly dark skies are essential if you want to take full advantage of this scope’s large aperture, high light transmission, and superb optical performance. This is not a scope that’s happy having its performance limited by a light-polluted suburban observing environment.

The scope is substantial in both size and weight. One very motivated individual can lift the 75-pound scope up onto its 50 lb. tripod, although probably with some difficulty and a few anxious moments. However, once on the tripod, a blind hole in the base of the scope has to be aligned with a blind hole and threaded rod in the top of the tripod to lock the scope in place. A second person to help lift and to steady the scope while you thread the rod into the scope base is almost essential to make the job easier and less adventurous in the dark.

If you have regular access to dark skies, and the size and weight of the scope isn’t an insurmountable obstacle, the 12” LX200-ACF with coma-free UHTC optics may be the last telescope you ever want or need to buy. It has high light transmission and all of the aperture you need to keep you busy observing and photographing for the rest of your life. And it has enough useful features to handle almost any observing and astrophotographic chore you set for it . . . at a price that’s surprisingly within reach.

This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.

This is the magnitude (or brightness) of the faintest star that can be
seen with a telescope. The larger the number, the fainter the star that
can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This
is the formula that we use with all of the telescopes we carry, so that
our published specs will be consistent from aperture to aperture, from
manufacturer to manufacturer. Some telescope makers may use other
unspecified methods to determine the limiting magnitude, so their
published figures may differ from ours.

Keep in mind that this
formula does not take into account light loss within the scope, seeing
conditions, the observer’s age (visual performance decreases as we get
older), the telescope’s age (the reflectivity of telescope mirrors
decreases as they get older), etc. The limiting magnitudes specified by
manufacturers for their telescopes assume very dark skies, trained
observers, and excellent atmospheric transparency – and are therefore
rarely obtainable under average observing conditions. The photographic
limiting magnitude is always greater than the visual (typically by two
magnitudes).

This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

This is the ‘speed’ of a telescope’s optics, found by dividing the focal
length by the aperture. The smaller the f/number, the lower the
magnification, the wider the field, and the brighter the image with any
given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally
best for lower power wide field observing and deep space photography.
Slow f/11 to f/15 focal ratios are usually better suited to higher power
lunar, planetary, and binary star observing and high power photography.
Medium f/6 to f/10 focal ratios work well with either.

An f/5
system can photograph a nebula or other faint extended deep space object
in one-fourth the time of an f/10 system, but the image will be only
one-half as large. Point sources, such as stars, are recorded based on
the aperture, however, rather than the focal ratio – so that the larger
the aperture, the fainter the star you can see or photograph, no matter
what the focal ratio.

This is the ability of a telescope to separate closely-spaced binary
stars into two distinct objects, measured in seconds of arc. One arc
second equals 1/3600th of a degree and is about the width of a 25-cent
coin at a distance of three miles! In essence, resolution is a measure
of how much detail a telescope can reveal. The resolution values on our
website are derived using the Dawes’ limit formula.

Dawes’ limit only
applies to point sources of light (stars). Smaller separations can be
resolved in extended objects, such as the planets. For example,
Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was
discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc
seconds!

The ability of a telescope to resolve to Dawes’ limit is
usually much more affected by seeing conditions, by the difference in
brightness between the binary star components, and by the observer’s
visual acuity, than it is by the optical quality of the telescope.

Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.

Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.

Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.

Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus.

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Clear skies,
Astronomics

The Meade 12” LX200-ACF has unique Advanced Coma-Free optics that put professional-grade visual and photographic performance in the hands of amateur astronomers at an affordable price.